Fitness Cost of Staphylococcal Cassette Chromosome mec in Methicillin-Resistant Staphylococcus aureus by Way of Continuous Culture

Abstract

We examined the effect of introducing type I or IV staphylococcal cassette chromosome mec (SCCmec) elements on the growth yield of Staphylococcus aureus in glucose-limited continuous culture. Type I showed increased glucose consumption and ATP demand per gram of cells synthesized and decreased cell yield compared to those of the parent strain. In contrast, type IV SCCmec elements had no adverse energetic effect.

Characterisation of virulence genes in methicillin susceptible and resistant Staphylococcus aureus isolates from a paediatric population in a university hospital of Medellín, Colombia

“…The findings of the present study are consistent with those of Collins et al (2010) because isolates harbouring SCCmec type I presented no or up to two virulence genes, whereas SCCmec type IV strains carried one or more virulence genes simultaneously, as observed in susceptible strains. The fitness cost on the growth and cell yield of S. aureus containing the SCCmec elements has also been experimentally demonstrated; the higher energy demand and decreased cell yield observed in SCCmec type I strains has not been observed in the SCCmec type IV strains (Lee et al 2007, Collins et al 2010). …”

The role of virulence determinants in community-associated MRSA pathogenesis

“…In contrast, the burden that other SCCmec allotypes (type I-III) impose on bacterial fitness (i.e. decreased in vitro growth rate [63]) has likely restricted traditional hospital-associated strains bearing these elements from spreading into the community. Hospital-associated MRSA seems to depend critically on high rates of antibiotic use in hospitals to overcome the fitness burden associated with the presence of antibiotic resistance elements.…”

“…Thus, it may impose only a slight cost to fitness, as it does not encode resistance determinants other than mecA. When comparing isogenic strains with different allotypes of the SCCmec element, type I SCCmec but not type IV SCCmec was found to impose a fitness cost to the bacterial host in terms of decreased in vitro growth rate and cell yield per mole of ATP consumed [63]. A highly discriminating rabbit co-infection model was used to further demonstrate that a USA300 clinical strain and its isogenic mutant with precise deletion of the type IV SCCmec exhibited no difference in infectivity of vital rabbit organs [34].…”

Offsetting virulence and antibiotic resistance costs by MRSA

“…Previous studies have shown that the relative fitness of hospital-acquired MRSAs carrying the type I SCCmec element is reduced (Ender et al, 2004), whereas strains containing the smaller type IV element were not affected (Lee et al, 2007). It has also been shown in vancomycin-resistant MRSA strains containing the type II SCCmec element that deletion of mecA compensated for some of the fitness costs associated with becoming vancomycin resistant, suggesting that mecA is also costly (Noto et al, 2008).…”